Turning 21 is a milestone. Of course, it means you can (legally) enjoy a beer or two, and you'll probably find your ideas are more easily welcomed into cynical adult discourse (lucky you).

Watching two members of the McLovins — guitarist Justin Berger and bassist Jason Ott — reach that age feels downright odd. They were barely teenagers when, in 2008, drummer Jake Huffman, Ott and guitarist Jeff Howard (who left in 2011) blasted a video of themselves doing Phish's "You Enjoy Myself" out into YouTube-world, grabbing eyeballs and earning some ink in Rolling Stone. (It's been viewed nearly a quarter-million times.)

As the McLovins – the name comes from a bespectled character's alias in the movie "Superbad" — they quickly gained a reputation as a must-see live act. The trio made the rounds on the festival circuit, opened for people like Buddy Guy and released three albums with Howard before he split to pursue other interests. Ott and Huffman didn't miss a beat, adding guitarist Atticus Kelly and Berger before the sun set on 2011; the quartet debuted on New Year's Eve in Hartford.

More than anything, Huffman says, the early media exposure sparked relationships with older artists that still smolder.

"We've made connections with a lot of people who've stayed with us as mentor-type figures," Huffman says. "[Phish lyricist] Tom Marshall, for example. We wrote songs with him three or four years ago. I can still call him if I have any questions about life or music, and that's true about a lot of people. We were the youngest band on the scene — still are, actually — and the other bands we play with are very helpful. They're excited to share their knowledge with us."

With Kelly and Berger fully integrated into the group, the McLovins face new challenges as they try to expand their fan base, which is already pretty big. They released "Beautiful Lights," their first studio album as a quartet, this past January before hitting the road on their first major tour of the South, playing 17 shows in 21 days. The 12 tracks on "Beautiful Lights" were recorded during long sessions at the Raritan, N.J. studio of Anthony Krizan, the former Spin Doctors guitarist, last spring.

The album begins and ends with thematically related songs, "Flavor of the Week" and "Birthday," which share a disco-flavored groove. In between you'll hear snapshots of various corners of American music, past and present: four-part a cappella gospel ("Cold Cold Iron"); Little Feat-worthy woo-woo soul ("Yankee Rose"); New Wave-ish, effects-heavy guitar textures and radio-friendly rock with lyrics about relationships gone awry (listen to "Tracy," for example); and other details.

What's noteworthy is the absence of any sort of electronic sounds, which have become popular with young jam bands.

"We've been listening to a lot of the Band and the Allman Brothers, some Steely Dan," Huffman says. "We've pulled sounds from older music, and we really try to keep that old-school feel. … I've realized that we want to stay with what we're good at, what comes from the heart, and at this point in our songwriting, there isn't a computer involved."

Huffman finds nothing wrong with the EDM scene, nor with bands that draw inspiration from it. "But I would rather go to the Gathering of the Vibes and hear Widespread Panic than be at a raging electronic music festival. I just personally connect more to organic forms of music."

One track on "Beautiful Lights," "Daze," has some of the long-form jamming they'll pull off onstage. Compared with other jam bands, however, the McLovins exercise restraint.

"We don't always go for the extended jams," Huffman says. "With a lot of other bands, every other song might have a jam in it." Their focus in recent years has been crafting concise, memorable songs, some of which may turn into jam vehicles.

"I wouldn't call us a jam band. Those are the groups we play with and those are the gigs that we book, but first and foremost we are songwriters. ... If we play 12 songs, maybe only three of those will have jams. We really save them, and that's what makes it special."

The album and recent Southern tour, Huffman says, are evolutionary steps forward. "This year has really been a breakthrough for us. That was the first and longest time we've been on the road, and that's when we realized that we could be a touring band. It was amazing and super-cool, being cooped up in a Jeep with other dudes, realizing what touring actually is."

They'll head out to Colorado this summer, and Huffman knows one trip isn't enough: relationships with out-of-state fans need to be maintained. And that means more tours and more new music to promote. Their upcoming show on Sunday, April 20, at Infinity Hall in Norfolk will be one of their last non-festival appearances in Connecticut for some time. "We're just not going to be here. We have other markets to hit now."

Huffman is wary of appearing too many times in his home state.

"Everybody in Connecticut was getting tired of us," he says. "If you didn't go to one show, you knew you could go to the next three. We overplayed the market, and we learned from that."

Through watching other bands, he's learned that there's no cookie-cutter way to be successful in the music business: Phish, for example, for their grass-roots model of fan involvement, or Radiohead, "because of how god-like they've made themselves," Huffman says. He's taken some online music-management classes through the Berklee College of Music, and he's learned the simple rules professional bands tend to follow: write songs for an album, record the album, go on tour. (That sounds like common sense, until you look around at all the local bands that aren't following that formula.)

"Minus the Bear toured and independently sold so many of their own records, and they just toured on their own for years," Huffman says. "A lot of bands do things differently… We see what they do, and we mish-mash it together until we've formed our own thing."

THE MCLOVINSperform on Sunday, April 20, at 7:30 p.m. at Infinity Music Hall & Bistro, 20 Greenwoods Road West, Norfolk, with the Interlopers. Tickets are $19 to $29. Information: infinityhall.com.